The Effect of Near-Wall Vortices on Wall Shear Stress in Turbulent Boundary Layers

Shuangxi Guo,Wanping Li

doi:10.4236/eng.2010.23027

Shuangxi Guo, Wanping Li

Open Access

https://doi.org/10.4236/eng.2010.23027

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Journal: Engineering	Publication Date: Jan 1, 2010
Citations: 19	License type: CC BY 4.0

Affiliation: Huazhong University of Science and Technology

Abstract

The objective of the present study is to explore the relation between the near-wall vortices and the shear stress on the wall in two-dimensional channel flows. A direct numerical simulation of an incompressible two-dimensional turbulent channel flow is performed with spectral method and the results are used to examine the relation between wall shear stress and near-wall vortices. The two-point correlation results indicate that the wall shear stress is associated with the vortices near the wall and the maximum correlation-value location of the near-wall vortices is obtained. The analysis of the instantaneous diagrams of fluctuation velocity vectors provides a further expression for the above conclusions. The results of this research provide a useful supplement for the control of turbulent boundary layers.

Highlights

The flow phenomenon of turbulent boundary layers is common in nature
The wall skin friction is closely related with the near-wall turbulent structures, so the researches on these two aspects are in accordance
The objective of the present study is to explore the relation between the near-wall vortices and the shear stress on the wall in two-dimensional channel flows

Summary

Introduction

The flow phenomenon of turbulent boundary layers is common in nature. It is closely related to aerospace, marine, environmental energy, chemical engineering and other fields. The wall skin friction is closely related with the near-wall turbulent structures, so the researches on these two aspects are in accordance. Instead of vertical to the wall, certain angles were presented between the blowing-suction direction and the streamwise direction This meant that the velocity boundary conditions brought by their control method were normal and streamwise velocities instead of normal and spanwise velocities. Their experiments showed a better effectiveness of wall shear stress reduction if the angle was proper [9]. As well as streamwise vortices, spanwise vortices are the main characteristics in turbulent boundary layers, while are they the crucial effect factors on wall shear stress as the streamwise vortices?

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Conclusion